This invention relates to a a combination counting and weighing system for weighing out a predetermined number of articles so as to have a total weight satisfying a predetermined condition.
Various combination counting and weighing systems have been proposed for weighing out a batch of articles having a predetermined number by a combination weigher which is originally adapted for weighing articles in a plurality of weigh units and combining the resultant weight values to obtain a desired total weight. In a system disclosed in Japanese patent publication gazette No. 55-48249, for example, a plurality of articles are weighed in each weigh unit of a combination weigher, the resultant weight value is divided by a reference unit weight of the articles to convert it into the number of articles, such numbers of articles are arithmetically combined to select combinations having a total number satisfying a predetermined condition and, separately, the corresponding weight values are similarly combined to confirm their total weights satisfying a predetermined condition. Although this system can attain the desired objective it is necessary to independently execute separate combination arithmetic operations for the number and weight and this results in a disadvantage in that two similar operation circuits will be needed if both operations are executed in parallel fashion, while the operation time will be doubled if they are executed in series fashion. Japanese utility model opening gazette No. 56-96331 and Japanese patent opening gazette No. 57-137820 disclose systems proposed to remove the above disadvantage. In the former system, the weight values are combined as they are without conversion into number and, separately, a predetermined total number values condition is multiplied by a reference unit weight to covert it into a total weight condition, thereby selecting a combination having a total weight satisfying this condition. In the latter system, the weight value from each weigh unit is converted into the number of articles and then rounded into an integer which is multiplied by the reference unit weight and converted again into the weight of articles. Such converted weight values are arithmetically combined to select a combination having a total weight corresponding to the predetermined number. Although these two improved systems have succeeded in some reduction of the above disadvantage, they do not avoid the problem that an error may occur in either the resultant total weight or number of articles.
In the above-mentioned system of Japanese patent opening gazette No. 57-137820, for example, a target weight W and a target number N are previously set. The weight value from each weigh unit is divided by a reference unit weight W/N for conversion into the number of articles which is then rounded into an integer. The rounded number is then multiplied by the reference unit weight W/N for re-conversion into a weight value. A normal combination operation is executed with such converted weight values, and then combined weight values are compared with the target weight to select an optimum combination. However, the combined weight values in this case generally deviate from the target weight and result in a reduced selection efficiency. This is because the rounding operation results in deviation of the number of articles from its true value when there is an abnormal difference between the average unit weight of articles in a specific weigh unit and the reference unit weight thereof. Therefore, the number of articles of the selected combination is sometimes inconsistent even if its total weight satisfies the condition.